Adenocarcinoma of the prostate, the second most common cancer to effect American males with a high incidence in non-white males, is amenable to local radiation therapy, with a suggestion that local control improves with advanced staging when proportionately higher doses of irradiation are employed. Because of the proximity of critical local structures, primarily the bladder anteriorly and rectum posteriorly, doses in excess of 7000cGy are associated with a significant increase in side effects and complications. Local failure has been associated with an increased incidence of metastatic disease, as well. In order to obtain higher tumor doses, relative to critical surrounding normal structures, treatment strategy which accurately locates the target volume and maximally shield surrounding normal tissue must be employed. Three dimensional conformal radiation therapy involves the use of three dimensional image reconstruction from various imaging modalities, usually CT-MRI to devise and execute treatment plans which maximally enhance the dosage difference between tumor and critical surrounding normal tissue. Sophisticated blocking is employed which on each of multiple planar or non-coplanar treatment portals closely conforms to the target volume, employing computer assisted custom blocks or multileaf collimators. In order to critically test the purported advantage of 3D CRT in prostate cancer, large scale clinical trials are required utilizing standardized methodology and techniques which need to be devised, and upgraded to employ state-of-the-art imaging and therapeutic technologies. The University of Miami, Department of Radiation Oncology has the experience in conformal radiation therapy and issues involving immobilization and localization, as well as the experience and patient volume treating prostate cancer, which coupled with multiple state-- of-the-art imaging, treatment planning, and therapy equipment will contribute to the development and evaluation of 3D CRT in a cooperative group setting.